This invention relates to medical devices for introducing catheters or the like into the body and in particular into blood vessels of the body.
Catheter assemblies provide a reusable conduit for the passage of catheters and other medical devices, e.g., guidewires, through the body flesh into blood vessels or other body passageways. Catheter assemblies are well known in the art. U.S. Pat. No. 5,098,392 granted to Amplatz et al. discloses an introducer assembly having (1) an introducer element consisting of an elongated tubular member defining an introducer sheath and an introducer hub disposed at the proximal end of the introducer sheath which further defines an introducer conduit along a longitudinal axis, and (2) a dilation element having an elongated tubular member defining a dilator having a tapered distal end portion and a dilator hub disposed at the proximal end of the dilator, which is sized so that the dilator may be inserted through the conduit of the introducer hub and introducer sheath and that the dilator tapered distal portion extends beyond the introducer sheath distal end.
Prior to the use of the catheter assembly, a needle is inserted through the body flesh and into a blood vessel, and a guidewire is inserted into the blood vessel through the center passage of the needle. The needle is then removed leaving the guidewire in place. The introducer assembly is then inserted over the guidewire such that the tapered distal portion of the dilator acts to gradually expand the puncture opening to ease the passage of the introducer sheath into the blood vessel. After the introducer sheath has been inserted to a desired depth within the blood vessel, the dilator element is removed from within the introducer element. A catheter can then be inserted through the introducer sheath into the blood vessel. In addition to introducer-dilator assemblies, other catheter assemblies include the combination of an introducer sheath with obturators, sterile sleeves, Tuohy-Borst fittings and the like.
To prevent or minimize the loss of blood or bodily fluid after the catheter assembly is in place, a hemostasis gasket is typically incorporated in the catheter assembly. U.S. Pat. No. 5,098,383 to Amplatz et al. describes such a catheter introducer assembly incorporating a hemostasis gasket. The hemostasis gasket is designed to form a seal after the dilator element or the like has been removed thereby preventing blood or bodily fluid from exiting from the introducer element. After the dilator element has been removed, the catheter which is to be inserted into the blood vessel must be carefully inserted into and guided through and past the hemostasis gasket. As the distance between the proximal end of the hub of the introducer sheath and the hemostasis gasket increases, the gasket becomes less accessible making it increasingly difficult to insert the catheter past the gasket. Moreover, if the catheter being used is of a curved or pigtail design, the difficulty of inserting the catheter through the hemostasis gasket is compounded, and at times requires the user to straighten the catheter with a guidewire prior to insertion.
During the initial insertion of the catheter assembly, the body's resistance to the expansion of the puncture opening exerts forces on the distal portion of the dilator tending to push the distal end of the dilator rearwardly in the proximal direction into the introducer sheath. In order to ensure that the tapered distal portion of the dilator remains extended beyond the blunt distal end of the introducer sheath during the initial insertion of the catheter assembly, the dilator hub is releasably connected to the introducer hub.
Several means for releasably connecting the introducer hub and the hub of the other component of the catheter assembly, e.g., the dilator hub, are known in the prior art. Unfortunately, with some of these prior art designs, the interconnected hubs are prone to becoming accidently disengaged. Moreover, because of the depth of the introducer hub and the distance between the proximal end of the introducer hub and the hemostasis gasket, insertion of certain catheters, particularly those having a curved or pigtail design, into the introducer sheath after the dilator element has been removed, is difficult.
A prior art means for releasably connecting the dilator hub and introducer hub comprises rotatably engaging studs and complementary slots associated with the dilator and introducer hubs. U.S. Pat. No. 4,192,305 to Seberg discloses a catheter placement assembly having a needle and lumen wherein the needle and lumen are mechanically engaged by complementary means associated with the needle and lumen hubs, such as tabs associated with one hub and slots associated with the other hub. U.S. Pat. No. 4,946,443 to Hauser et al. discloses a catheter assembly having a releasable connecting means having a pin or stud associated with one hub that is received by a slot associated with the other hub. Medical assemblies having releasable connecting means of the pin-and-slot type are also disclosed in U.S. Pat. No. 4,609,370 to Morrison; U.S. Pat. No. 4,986,814 to Burney et al.; and U.S. Pat. No. 3,860,006 to Patel. These types of rotatably engaging releasable connecting means do not have a stop means for securely locking the pin within the slot and, therefore, are prone to accidental disengagement through the inadvertent rotation of the dilator hub.
Additionally, U.S. Pat. No. 5,098,393 to Amplatz et al. discloses that the dilator hub and introducer hub may be releasably connected by an axially engaging snap fit or friction fit connection. An axially aligned snap fit connection of the type disclosed in U.S. Pat. No. 5,098,393 is prone to accidental disengagement through the inadvertent application of a transverse force to the proximal end of the dilator hub. Moreover, while the axial alignment of the dilator and introducer hubs is maintained with such a releasable connection, rotational movement between the dilator and introducer hubs is permitted.
Upon an accidental disengagement of the dilator hub and introducer hub during the initial insertion of the catheter assembly, the tapered distal end of dilator would migrate proximally into the introducer sheath and the blunt distal end of the introducer sheath may be forced against the blood vessel. In that event, trauma to the blood vessel and body flesh surrounding the puncture site could result. Such trauma may result in the procedure being reinitiated at another location along the blood vessel or being abandoned altogether. Accidental disengagement of an obturator can result in kinling of the introducer sheath thus preventing further use of the sheath and requiring replacement with a new sheath. Similarly, disengagement of a sterile sleeve from the introducer sheath will compromise the required sterile environment. Further, disengagement of the Tuohy-Borst fitting from the introducer sheath can cause the catheter, which is received by the fitting and within the introducer, to move from its desired position in the patient.
An improved catheter assembly is disclosed in U.S. Pat. No. 5,391,152 to Patterson. This catheter assembly has an improved releasable interlock connection which comprises a first element having a hub with outwardly protruding radial tabs disposed at the distal end of the hub and a second element having a hub with two complementary slots and two interference fit protuberances disposed at the proximal portion of the second element hub A- which rotatably receive and secure the first element tabs. While the catheter assembly disclosed in U.S. Pat. No. 5,391,152 provides an improved "locking mechanism" when Adcompared to the "snap-fit" or "press-fit" interlock designs previously described in the art, the depth of the introducer hub and distance between the proximal end of the introducer hub and the hemostasis gasket makes insertion of a curved or pigtail catheter difficult.
Accordingly, it is an object of the present invention to provide a catheter assembly with a first and second catheter element (e.g., a dilator and an introducer, respectively), each element having a hub with an improved rotatably engageably releasable interlock connection and a rotational securement means which minimizes, and preferably eliminates, the risk of accidental disengagement of both the axial and rotational alignment of the first and second catheter element hubs. It is a further object of this invention to provide a catheter assembly having a reduced distance between the proximal end of the second catheter element hub (e.g., introducer) and the hemostasis gasket thereby permitting the catheter assembly to have a lower profile. A catheter assembly having a lower profile makes it easier, once the first catheter element (e.g., dilator) is inserted into the body and the second catheter element (e.g., introducer) removed, to insert a curved or pigtail catheter into the body through the second catheter element (e.g., introducer).